OK Duke Ellington or Louis Armstrong can obviously be called central figures of jazz, so can Charlie Parker or whoever. They made and defined the genre.
You can hardly call Pete Seeger or Martin Carthy or Vaughan Williams or Sean O Riada or whoever defining figures of folk, they took the material, worked with it, made new things out of it, but they weren't OF it. They heard it, fell in love with it, and lived with it. . Wonderful musicians, but they didn't MAKE it. It was there, made by someone else. Not by people you could put individdual names to. Just made by an innumerable number of people working together.